There is a need today for creating a low radar signature for different objects such as e.g. aircrafts, i.e. to design aircrafts having a low radar visibility. Significant progress has been achieved in a number of problem areas as e.g.:                Intake/exhaust        Cockpit/canopy        Hull or fuselage shape        Absorbers        Armamentbut there is often a problem with reducing the passive signature of the aircraft sensors such as antennas.        
A number of solutions have been proposed to achieve antennas with a low Radar Cross Section, RCS. The RCS value for an object depends on its size, shape, reflectivity and direction of the signal reflected from the object.
It is now familiar to most that a flat-plate antenna on a mechanical turntable is a major contributor to the RCS value of any fourth-generation fighter. A flat plate antenna is a passive, slotted waveguide antenna with a thin RF distribution network. Another way to put it is that there is limited reason to embark on a costly RCS reduction programme of a 4G aircraft as long as the flat-plate remains in place. It is also well-known that an Active Electrically Scanned Antenna (AESA) offers a lower RCS value than the flat-plate antenna.
However, it is not widely known that the RCS of an ordinary AESA is too high for any aircraft with substantial, low-RCS enabled abilities. This means that the tactics, number of aircraft, and other resources needed for an AESA-equipped 4G aircraft are comparable to what is required for a flat-plate 4G aircraft—mission for mission.
A stealth AESA, on the other hand, has an RCS so low that it enables an aircraft—provided the aircraft itself has a low RCS—to perform missions previously regarded out of reach for a 4G aircraft.
Most of the problems with existing stealth AESA solutions have been given unique solutions leading to high complexity, and consequently, a high cost. In some cases the performance is also limited. Some main problems are:                Difficulties to achieve wide-band matching.        Complexity is added by the introduction of absorbers for cross-polarized incident waves to an already complex antenna. Since it needs to support itself (or to be mounted against a supporting surface) against vibrations over the large aperture, complicated mechanical problems arise, especially since the absorber needs to be slotted.        A separate solution is required for absorption at the AESA side surfaces and at the base surface in order to reduce scattering adding further to the overall complexity.        Diffuse scattering from the antenna aperture.        The conventional hermeticity solution with a laminate cover worsens the RCS. The laminate cover needs to support its own mass against e.g. vibrations. This leads to a thickness that result in limitations of scannability and bandwidth.        
There is thus a need to achieve a low RSC AESA for objects or vehicles such as fighters and missiles while at the same time offering improved handling and mechanical stability.